| dc.description.abstract | Service vessels within the aquaculture industry are normally designed as catamarans, however, the ships experience large resistance, where the contribution from wave resistance is dominant. In order to increase the ship speed and lower the resistnace, it is looked at the possibility of changing the ship hull from a catamaran to a trimaran.
An overview of ship resistance theory is given along with a solid Computational Fluid Dynamics background. A method based on RANS equations and $k-\omega$ SST turbulence modelling has been developed and the code has been tested on a cylinder in axial flow with different submergence depths. The resulting mean value of the drag coefficients agrees well with literature.
Resistance analysis for the trimaran hull with incoming uniform fluid velocity equal to $10$ knots has been done. OpenFOAM v1712 is used to perform the simulations. The mesh is generated by using \textbf{blockMesh} and \textbf{snappyHexMesh}. The simulations of the trimaran hull were run on Vilje using 32 processors. The cylinder test case were run on the CFD2 computer at the Department of Marine Technology at Tyholt.
Resistance data for a catamaran vessel with similar volume displacement and approximately the same $L_{OA}$ is used for comparison. The resistance force computed for the catamaran is equal to $32$ kN. The resistance force obtained from the simulations is approximately equal to $26$ kN. The fluid flow in the trimaran simulation did not stabilise due to limited time to run the simulation. Thus, the resistance data are concluded to be not sufficiently reliable to proceed in the design process. However, the setup can be used as a basis for further work which can be a valuable contribution to the design process along with model testing. | |
